The significance of the blockage mitigation problems in information transmission has been addressed and identified by many for example: The U.S. Department of Defense components advocate mobile satellite communications. In 2004 the Air Force issued a request for proposal for 40 Gbps laser satellite communications with severe transmission degradation. The Army established the Future Combat System/Objective Force (FCS/OF) including satellites in 2003. The Navy requested innovative technologies in 2002 to support reliable and time critical multimedia information transmission for ships on the sea and submarines under the sea, where transmission channel characteristics are different. All components-addressed in satellite controlled UAVs (unmanned air vehicles), where operational hostile environment is unpredictable.
Particular difficulty includes a satellite communication-on-the-move that encompasses acknowledgement-based protocols to recognize severe disruption in service and to employ appropriate correction techniques. Protocol analysis needs to ensure signal quality is maintained in the presence of errors during transmission, as well as maintaining quality of service (QoS) if the signal is blocked. An optimal solution is always sought to maintain QoS within the network. Demands for optimal solutions have not been met due to the difficulty of the problem. Existing techniques are neither adequate nor optimal.
All transmission-blocking phenomena are time dependent and probabilistic. Previous studies have documented actual measurement by NASA/JPL of the Advanced Communications Technology Satellites (ACTS) Ka-band under heavy shadowed environments and have concluded that the 1% fade factor for Ka-band is well in excess of 30 dB, and may be as high as 45 dB. When a channel is multipath, space-time coding with multiple antennas can be useful. Among the well-known solutions is BLAST (Bell Laboratories Layered Space Time), which has multiple antennas. The idea of BLAST is to demodulate the desired signal and remove the rest, but, error propagation exists and ordering in detection is necessary.
Trellis Coded Modulation (TCM) has been advocated, but for a simple 6 bits per vector with 4 transmit antennas, the state complexity is 218. For Turbo decoding, impressive performances can only be obtained for code length of 10,000 bits with multiple (typical 8 to 10) iterations, and with a posteriori probabilistic or maximum likelihood decoding, which complicates both timing and equipment. Most significantly, what happens if the high-frequency transmission channel is not multipath, Gaussian, Rayleigh, or Ricean fading, and has no meteor insight? What happens if the transmission is completely blocked due to mountain tunneling or concrete jungles?
The above examples illustrate the fact that needs existed and solutions sought. Prior arts limited to Ad Hoc fix leaking bucket approaches. Non-optimal solutions applied only to separate systems of wired or wireless, applicable only to specific degraded transmission channel conditions, or particular frequency range. This invention breaks through such limitations of related art with fundamental results independent of transmission media and operating frequencies with enhanced capabilities in blockage mitigation systems.
For ARQ system evaluation, Peterson and Weldon (Error Correcting Codes, MIT Press, 1972) addressed the issue of the probability of an undetected error for block codes used in error detection. By the weights of code words in Hamming codes, the undetected error probability in a binary symmetric channel can be established through the corresponding weight-enumerating polynomial. In practice, it is very difficult to obtain the weight enumerators even with the help of MacWilliam's and Pless's power moment identities (The Theory of Error-Correcting Codes, North-Holland, 1977). This invention constructs system efficiency and error probability formulations for all ARQ/FEC based systems evaluations without weight enumeration for unequal terminal capabilities in the transmission network.